Allow for search in dropdown

What does this MR do and why?

Allow for search in dropdown

• allow users to search for groups outside of first page
• populate dropdown with existing ids if they are not retrieved in the first page
• policy drawer will need a similar change, but that will come in another MR
• if a user updates the yaml and navigates back to rule mode, we need to request any added ids that have not been retrieved already
• refactor to move this logic into the utils
• update tests

References

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MR acceptance checklist

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Screenshots or screen recordings

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Before	After
No search and if the selected ids where not on the first page, they were not selected	searchable_groups_small update_search_small

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Upload a GitLab Ultimate license
2. Enable the feature flag echo "Feature.enable(:scan_result_policy_block_group_branch_modification)" | rails c
3. Navigate to a group => Secure => Policies => New policy => Merge request approval policy
4. Verify the Block group branch modification group selection is search able
5. Navigate to yaml mode and modify the ids
6. Navigate to rule mode and ensure the new ids are selected

Related to #500842 (closed)